Starter drive for combustion engines

ABSTRACT

An axially shiftable rotatable rod is mounted with radial clearance in the hollow output shaft of a motor. A pinion is fixed on the rod and at least in part located outwardly beyond the shaft so that it can mesh with a gear of a combustion engine to be started. A sleeve surrounds the rod fixed with the pinion and has an outer steep-pitch thread. A motion-transmitting coupling is provided including a first coupling element mounted in the shaft for rotation therewith and a second coupling element carried by the sleeve for rotation therewith. The coupling elements are provided with mechanically interlockable coupling projections and damping means is located between the sleeve and the first coupling portion and serves for damping axially directed forces.

United States Patent Vogelet al.

STARTER DRIVE FOR COMBUSTION ENGINES Erich Vogel, Bernhausen; Gunther Ullmann, Schwieberdingen, both of Germany Robert Bosch Gmbl-l, Stuttgart, Germany Oct. 16, 1970 Inventors:

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data Nov. 11, 1969 Germany 19 56518.5

US. Cl ..74/6

Int. Cl ..F02n 1 1/00 Field of Search ..74/7 R, 7 A, 6, 7 B

References Cited UNITED STATES PATENTS 5/1943 Fitzgerald ..74/6

[451 May 23,1972

2,422,319 6/1947 Thompson ..74/7

Primary Examiner-Milton Kaufman Attorney-Michael S. Striker 57 ABSTRACT An axially shiftable rotatable rod is mounted with radial clearance in the hollow output shaft of a motor. A pinion is I fixed on the rod and at least in part located outwardly beyond .the shaft so that it can mesh with a gear of a combustion engine to be started. A sleeve surrounds the rod fixed with the pinion and has an outer steep-pitch thread. A motion-trans- I mitting coupling is provided including a first coupling element mounted in the shaft for rotation therewith and a second coupling element carried by the sleeve for rotation therewith. The coupling elements are provided with mechanically interlockable coupling projections and damping means is located between the sleeve and the first coupling portion and serves for damping axially directed forces.

10 Claims, 1 Drawing Figure PATENTEUMAYZS 1972 3, 664.201

INVENTOR 511a 006e'6 Gaunt! UM/IIIW ATTORNEY BACKGROUND OF THE INVENTION The present invention relates generally to starter drives, and specifically to starter drives for combustion engines.

Various different types of starter drives for combustion engines are known, including a sliding type having a positively driven and a following coupling portion, which are constructed as friction disks which are slid or pushed into frictional abutment with one another for motion-transmitting purposes, when the starter drive is energized. The present invention is concerned with this type of starter drive, where two coupling portions or coupling elements are brought into motion-transmitting engagement.

It has been found in the aforementioned prior-art constructions that a significant amount of wear occurs on the friction disks even after a relatively short period of use; particularly where starter motors of relatively high capacity are involved, this can quite rapidly lead to damage to the friction disks of such magnitude that one or both of them will break.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome these disadvantages.

More particularly it is an object of the present invention to provide an improved starter drive of the type under discussion which is not possessed of these disadvantages.

A concomitant object of the invention is to provide such an improved starter drive which is capable of withstanding high stresses, such as for instance occur during starting of rapidly rotating direct-injection diesel engines, and which has a long life and is highly resistant to wear.

Still another object of the invention is to provide such an improved starter drive which is simple in its construction.

In pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention resides in a starter drive for combustion engines which, briefly stated, comprises a motor having a hollow output shaft and an axially shiftable rotatable rod mounted with radial clearance in this shaft. A pinion is fixed on the rod and at least in part extends outwardly beyond the shaft so that it can mesh with a gear which in turn is intended to transmit motion to the combustion engine to be started. A sleeve surrounds the rod fixed with the pinion and has an external steep-pitch thread. Motion-transmitting coupling means is provided including a first coupling element mounted in the shaft for rotation therewith, and a second coupling element carried by the sleeve. Cooperating interlockable coupling portions are provided on the coupling elements and damping means is located between the sleeve and the first coupling portion and is operative for damping axially directed forces.

With the present invention we obtain a starter drive in which all components for motion transmission, both the components which connect the one coupling element with the shaft as well as the components which connect the two coupling elements with one another when motion is to be transmitted, are relatively far spaced from the axis of rotation of the output shaft of the motor, which is advantageous because this feature in conjunction with the provision of the damping means which substantially reduces the torque peaks acting upon the drive when the starting operation begins and the stresses acting upon .the drive when the teeth of the pinion first move into mesh with the teeth of the engine-associated gear, the resistance to wear and thereby the life of the drive are substantially increased over what is known from the prior art.

The novel features which are considered as characteristic for the invention are set forth in particular inthe appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a partially broken-away, partially longitudinally sectioned fragmentary illustration of one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing in detail it is pointed out that reference numeral 39 identifies a rotatable gear having an outer annulus of gear teeth, and being connected in suitable manner with a combustion engine which is to be started. The combustion engine and the axis of rotation of the gear 39 have not been illustrated, nor has the gear 39 itself been illustrated in more than fragmentary form. The reason for this is that the gear 39, its arrangement and its connection with a combustion engine, are all entirely conventional and neither form a part of the present invention nor present any problems of understand ing to those skilled in the art. The present invention is concerned solely with the novel starter drive which can be substituted in toto for any prior-art starter drive of the type driving a gear which in turn is connected in motion-transmitting relationship with a combustion engine. Therefore, the cooperation of the novel starter drive with such a gear and with such a combustion engine will be readily understood by those having ordinary skill in this field.

Coming to details of the FIGURE, it will be seen that reference numeral 10 identifies a fragmentarily illustrated, electrically operable starter motor 10 surrounded by a housing 11 whose open side is closed by a bearing flange 12. The motor 10 in this embodiment is of the type which can be energized to turn over at a low number of rotations per minute, as well as being capable of energization for turning over at a high number of rotations per minute. Again, the manner in which this is done is well known to those skilled in the art and is thereforenot believed to require a separate description.

The output shaft 13, which is rotated when the motor 10 is I energized, is hollow and has secured to it a cup-shaped entrainment member or driver 14 the open side of which is closed by a closure member 15 which in turn is tumably journalled in the flange 12 by means of a ball bearing 16.

An axially shiftable rod 17 extends through the hollow output shaft 13, the cover 15 and the flange 12, and carries for rotation with it a pinion l8 and a sleeve 20 which is non-' rotatably connected with the pinion 18 by the key 21 and provided on its outer circumferential surface with a steep-pitch thread 19 as illustrated. A nut 22 fixedly connects the pinion l8 and sleeve 20 with the rod 17. Y

A roller bearing 23 journals the sleeve 20 in the flange l2,

and a needle bearing 24 journals the sleeve 20 in the hollow anchor shaft 13; thus, the sleeve 20 is both rotatable and axially shiftable together with the pinion and the rod 17.

An annular member 25 surrounds that portion of the sleeve 20 which is provided with the steep-pitched thread 19 and is provided with a correspondingly pitched internal thread meshing with the thread 19. The member 25 constitutes the driven part of a coupling for motion-transmitting purposes between the motor 10 and the pinion 18. The counterpart, that is the driving part of the coupling, is in form of an annular disk or plate 26 which is slidably accommodated on a hub 27 of the annular member 25 and provided on its circumference with at least one but in the illustrated embodiment several radial projections 28. The driver 14 is provided with a plurality of circumferentially distributed longitudinal slots 29, the number of such slots evidently corresponding to the number of projections 28, and the projections 28 each are received with some play in the respective slots 29 and have freedom of movement axially of the slots 29 and therefore of the shaft 13.

As the drawing shows, the facing end faces of the members 25 and 26 are each provided with an annulus of sawtoothshaped coupling projections or teeth 30a and 30b, respectively, and these are normally urged into meshing engagement by the biasing force of a helical spring 32 which bears upon the member 25 and an abutment ring 31 mounted on the sleeve 20.

According to the present invention there is also provided damping means, here in form of a plurality of disk springs 33 which abut against a shoulder 34 provided on this purpose on the sleeve 20. The coupling member 26 in turn abuts against the springs 33 with that one of its axial end faces which is remote from the one provided with the teeth 30b. The teeth 30a of the member 25 and the teeth 30b of the member 26 together constitute an overrunning clutch which permits a relative rotation of the pinion 18 and the output shaft 13 when the combustion engine has started and, turning over under its own power, rotates the pinion 18 with a number of revolutions higher than that of the shaft 13.

The disengagement of the teeth 30a, 30b upon operation of the coupling as an overrunning clutch is assisted by a centrifugal separating device located between the members 25 and 26 and composed of a ball cage 35, balls or spherical members 36 and a conical ring 37. Of these, the ball cage 35 is fixedly accommodated in a recess 38 of ring-shaped outline in the member 25; the balls 36 are accommodated in the cage 35 and the conical ring 37 is fastened in a recess 39 provided on that end face of the member 26 which is directed towards the member 25. The inner conically diverging surface 40 of the ring 37 engages the balls 36 and the components are so configurated and dimensioned that even when the teeth 30a, 30b are fully in engagement with one another, the balls 36 are retained axially without play between the cage 35 and the ring 37.

The operation of the novel starter drive according to the present invention will already be understood from what has been set forth above.

Energization results from the energization of a non-illustrated displacing relay which causes the rod 17 with the sleeve 20 and the pinion 18 to shift axially towards the gear 39 of the non-illustrated combustion engine to be started. At the same time the motor is energized at reduced voltage so that the shaft 13 rotates slowly with its rotation being transmitted via the driver 14, the member 26, the teeth 30b and 30a, the member 25, the thread 19, the sleeve 20 and the key 21, to the pinion 18. The pinion 18 thus is in slow rotation as it is advanced against the gear 39 with which it is intended to cooperate. If, now, a tooth of the pinion l8 abuts in end-toend relationship against a tooth of the gear 39, so that the teeth cannot immediately move into mesh, then the pinion 18 turns slowly with reference to the gear 39 until its teeth can move into meshing engagement with those of the gear 39, that is until such time until the teeth of the pinion 18-which continues to be urged forwardly in direction towards the gear 39can move into the spaces between the teeth of the gear 39. The axially acting forces which result on engagement between the pinion l3 and the gear 39, and on initial rotation of the latter, are substantially damped by the presence of the damping means in form of the springs 33 located between the sleeve 20 and the member 26.

On the other hand, if an end face of a tooth on the pinion contacts an end face of a tooth on the gear 39, in which latter tooth a groove or kerf has been formed due to wear, then the pinion is not capable of turning with reference to the gear 39 and the starting process must be repeated.

Once the teeth of the pinion 18 mesh fully with the teeth of the gear 39, a non-illustrated main current switch is closed, that is the motor 10 is now fully energized and the shaft rotates at higher speed whereby the pinion 18 turns over the combustion engine via the gear 39, until such time as the combustion engine begins to turn over by itself. Once this takes place, it will be the gear 39 which accelerates the pinion 18, so that the latter now turns faster than the shaft 13 of the motor 10. As a result of this, the pinion exerts a circumferential force via the thread 19 and trailing flanks of the teeth 30a, on the teeth 30b of the member 26 whereby the load acting upon the teeth 30a, 30b is reversed and because of their sawtoothshaped configuration and the action exerted by the steeplypitched thread 19, on the member 25, the teeth 30a, 30b separate against the urging of the spring 32 so that the pinion 18 can turn freely with reference to the shaft 13. This separation is facilitated and speeded by the centrifugal separating device described, because at increasing rotation the balls 36 are pressed outwardly by the centrifugal force resulting in axial displacement of the member 25 counter to the force of the spring 32, so that the teeth 30a and 30b become separated more quickly and more reliably.

It will be understood that each of the elements described above may also find a useful application in other types of constructions differing from those types described above.

While the invention has been illustrated and described as embodied in a starter drive for combustion engines, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A starter drive for combustion engines, comprising a motor having a hollow output shaft; an axially shiftable rotatable rod mounted with radial clearance in said shaft; a pinion fixed on said rod and at least in part extending outwardly beyond said shaft; a sleeve surrounding said rod fixed with said pinion and having a steep-pitch external thread; motion-transmitting coupling means, including a first coupling element mounted on said sleeve for rotation therewith and having an axially extending hub, and a second coupling element carried by said hub; cooperating interlockable coupling portions on said coupling elements; and damping means between said sleeve and second coupling element and operative for damping axially directed forces.

2. A starter drive as defined in claim I, said sleeve having a radial outer shoulder proximal to said pinion intermediate the same and said thread; and wherein said damping means comprises annular spring means surrounding said sleeve and abutting against said shoulder.

3. A starter drive as defined in claim 1, said coupling portions of said first and second coupling elements being constructed and configurated for cooperation in the manner of an overrunning clutch.

4. A starter drive as defined in claim 1; further comprising centrifugal means between said coupling elements and operative for effecting disengagement of said coupling portions under predetermined operating conditions.

5. A starter drive as defined in claim 4, said centrifugal means comprising a recess of circular outline provided in an axial end face of said first coupling element which is directed towards said second coupling element, a cage received in said recess and accommodating at least two equi-angularly spaced spherical members, and a conically configurated ring fixed with said second coupling element extending into said recess and having an inner circumferential surface contacting said spherical elements and conically diverging towards said first coupling element.

6. A starter drive as defined in claim 1 said second coupling element being an annulus and having an axially directed end face facing towards said first coupling element; and wherein said coupling portions are first coupling projections on said end face and second coupling projections on said first coupling element.

7. A starter drive as defined in claim 11; said motion-transmitting coupling means further comprising an impeller member rotatable with said shaft and in engagement with said second coupling element.

8. A starter drive as defined in claim 7, wherein said impeller member has at least one slot extending axially of said 10. A starter drive as defined in claim 9, said biasing means comprising a helical spring having opposite ends one of which bears upon said first coupling element, and an annular abutment on said sleeve at a side of said first coupling element which is axially remote from said second coupling element, the other end of said spring bearing upon said abutment means. 

1. A starter drive for combustion engines, comprising a motor having a hollow output shaft; an axially shiftable rotatable rod mounted with radial clearance in said shaft; a pinion fixed on said rod and at least in part extending outwardly beyond said shaft; a sleeve surrounding said rod fixed with said pinion and having a steep-pitch external thread; motion-transmitting coupling means, including a first coupling element mounted on said sleeve for rotation therewith and having an axially extending hub, and a second coupling element carried by said hub; cooperating interlockable coupling portions on said coupling elements; and damping means between said sleeve and second coupling element and operative for damping axially directed forces.
 2. A starter drive as defined in claim 1, said sleeve having a radial outer shoulder proximal to said pinion intermediate the same and said thread; and wherein said damping means comprises annular spring means surrounding said sleeve and abutting against said shoulder.
 3. A starter drive as defined in claim 1, said coupling portions of said first and second coupling elements being constructed and configurated for cooperation in the manner of an overrunning clutch.
 4. A starter drive as defined in claim 1; further comprising centrifugal means between said coupling elements and operative for effecting disengagement of said coupling portions under predetermined operating conditions.
 5. A starter drive as defined in claim 4, said centrifugal means comprising a recess of circular outline provided in an axial end face of said first coupling element which is directed towards said second coupling element, a cage received in said recess and accommodating at least two equi-angularly spaced spherical members, and a conically configurated ring fixed with said second coupling element extending into said recess and having an inner circumferential surface contacting said spherical elements and conically diverging towards said first coupling element.
 6. A starter drive as defined in claim 1, said second coupling element being an annulus and having an axially directed end face facing towards said first coupling element; and wherein said coupling portions are first coupling projections on said end face and second coupling projections on said first coupling element.
 7. A starter drive as defined in claim 11; said motion-transmitting coupling means further comprising an impeller member rotatable with said shaft and in engagement with said second coupling element.
 8. A starter drive as defined in claim 7, wherein said impeller member has at least one slot extending axially of said shaft, and wherein said second coupling element is annular and provided on its periphery with at least one radially projecting engagement portion received and guided with slight play in said slot.
 9. A starter drive as defined in claim 1, said coupling portions comprising first and second coupling projections; and further comprising biasing means normally biasing said first and second coupling projections to interlocking engagement.
 10. A starter drive as defined in claim 9, said biasing means comprising a helical spring having opposite ends one of which bears upon said first coupling element, and an annular abutment on said sleeve at a side of said first coupling element which is axially remote from said second coupling element, the other end of said spring bearing upon said abutment means. 